Water Quality and Aquatic Ecosystem Assessment Using Water Quality Indices in West Africa: Challenge and Perspectives

“Water quality is health” as it is said, “water is life.” The water quality and aquatic ecosystem health assessment is essential for early detection of water habitat degradation and overall aquatic ecosystem disturbances. All water management programs/agencies need simple and cheaper tools for water quality assessment. However, in West Africa there is an urgent need of water quality assessment tools, as far they are very limited. This chapter presents water quality indices as simple and cost-effective tool to monitor water quality. We explore the categories of water quality indices (WQIs), their use/application, and their scope in West African countries. We found that some multimetric indices (MMIs) are developed in West Africa, but they are not well known/used by local water managers and decision makers. There are not yet biotic indices (BIs) and physicochemical water quality indices (PCQWIs) typical to Western African countries areas, but most of them are applied/adapted to meet the needs of West African water quality and ecosystem health assessment. In this chapter, we present the results of some studies led in some West African countries regarding water quality indices (MMIs, BIs, PCWQIs), and address challenges and perspectives for long-term management of water and biological resources in developing countries

Kinetics of the Adsorption of Chromium(VI) Ions from Water by Vegetable Precursors Treated with Sulphuric Acid

The removal of chromium(VI) ions from water and wastewater through the use of activated maize cob (AMC) and activated banana peel (ABP) has been studied. In addition, the kinetics of the adsorption of Cr(VI) ions onto AMC and ABP were investigated. The effects of altering the initial Cr(VI) ion concentration, contact time and temperature on the removal process were studied. The removal of Cr(VI) ions increased with increasing temperature and depended on the initial Cr(VI) ion concentration, with complete removal being effected after a contact time of 80 min and 600 min for AMC and ABP, respectively. The process of Cr(VI) ion removal followed pseudo-second-order kinetics with the rate constants being determined at different temperatures in the range 20–40 °C. The activation energies for the adsorption of Cr(VI) ions onto AMC and ABP were calculated as 56.74 kJ/mol and 86.47 kJ/mol, respectively. Thermodynamic parameters such as the standard Gibbs' free energy change (Δ ads G 0 ), the standard entropy change (Δ ads S 0 ) and the standard enthalpy change (Δ ads H 0 ) were calculated. The thermodynamic studies revealed that the values of Δ ads H 0 were positive, suggesting that the adsorption process was endothermic in nature

STUDY OF COOKING PARAMETERS ON THE DEGRADATION OF ASCORBIC ACID CONTAINED IN GREEN LEAFY VEGETABLES PRODUCED AND CONSUMED IN THE KARA REGION-TOGO

<p>The purpose of this study is to quantify the content and investigate the effects of cooking temperature and time on the variability of vitamin C content in six green leafy vegetables: Solanum macrocarpon, Hibiscus sabdarifa, Octimum gratissimum, Vernonia amygdalina, Adansonia digitata and Corchorus olitotius. Two methods were used to determine the vitamin C contents of the samples processed by blanching and boiling at different cooking times. With the iodometric method, Hibiscus sabdarifa (0.5368 mg/g) and Adansonia digitata (0.5016mg/g) have the highest vitamin C contents, while Octimum gratissimum has the lowest concentration of 0.1760 mg/g. The results of quantification obtained by the spectrophotometric method present practically the same results as those of the iodometric method with as light decrease of 0.0242 mg/g for Hibiscus sabdarifa and an increase of 0.0147 mg/g for Adansonia digitata. The results of the study of the effect of temperature and cooking time, whatever the method, showed with the blanching, a loss of rate of 30,21% in vitamin C for Hibiscus sabdarifa and Solanum macrocarpon a loss of rate of 4,25%. The degradations were more considerable during the boiling of 15 min with maximum losses in the order of 79,05% for the leaves of baobab boiled and 45,24% respectively for Adansonia digitata and Solanum macrocarpon.</p><p> </p&gt

Traitement d'une eau naturelle polluée par adsorption sur du charbon actif (CAK) préparé à partir de tourteaux de karité

The study concerns organic and inorganic pollutants and its removal from natural water (Be Lagoon) using activated Shea cake (CAK). The activated carbon CAK has the following characteristics: BET surface area is equal to 1148 m2.g-1 and the pore volume is equal to 0.607 cm3.g-1. This activated carbon is essentially microporous with the volume of micropores representing over 70% of the total pore volume. The “batch method" was used for pollutant removal and it reveals that the contact time values are equal to 10 h for BOD and 15 h for COD. A systematic study was done to assess the influence of the mass of activated carbon on its adsorption capacity of BOD and COD. The Langmuir and Freundlich isotherm models agreed with experimental data. The maximum adsorption capacity obtained using Langmuir isotherm model was 12.66 mg/g for all the organic and inorganic pollutants and 11.24 mg/g for organic pollutants only.Le présent travail a pour but l'utilisation d’un charbon actif (CAK) préparé à partir de tourteaux de karité pour l'adsorption de polluants organiques et inorganiques d’une eau naturelle (lagune de Bè). Le charbon actif CAK présente une surface BET de 1148 m2.g-1 et un volume poreux de 0,607 cm3.g-1. Il est essentiellement microporeux avec un volume de micropores représentant plus de 70 % du volume total des pores. L’étude de laboratoire menée en batch a permis de déterminer des temps de contact optimaux de 10 h pour les polluants organiques seuls et 15 h pour l’ensemble des polluants organiques et inorganiques. L’influence du dosage en charbon actif sur les performances d’adsorption a également été étudiée. L’établissement des isothermes d’adsorption a montré que l’adsorption de l’ensemble des polluants organiques et/ou inorganiques est bien décrite par les modèles à l’équilibre de Langmuir et de Freundlich. Dans les conditions expérimentales utilisées, les capacités maximales d’adsorption des polluants par gramme de charbon actif ont été déterminées respectivement égales à 12,66 mg/g pour l’ensemble des polluants organiques et inorganiques et à 11,24 mg/g pour les polluants organiques